Cancer Immunology & Flashcards
Are mutations sufficient to have cancer?
What experiment answered this question?
Mutations are necessary for cancer, but are NOT sufficient on their own
It is common to fin tumours at autopsy, when people die from other causes and theses tumors never grew.
Experiment:
Injected rous Sarcoma Virus into chicks → got tumour at the site of injection, but not elsewhere even if injected in the circulation
Injected rous Sarcoma Virus into chicks that also had a 2nd site of inflammation (wound) → got 2 sites of tumor growth
Conclusion: The structure and composition of the tissue (i.e. the microenvironment) is important to control the growth of mutated cells.
If it becomes compromised (e.g. inflammation resulting from a wound), the transformed cells can grow.
Do we have evidence that in human, a compromised microenvrionment is associated with tumor growth?
YES
If the microenvironment is compromised (e.g. inflammation), transformed cells can grow (not direct correlation, more associative)
Ex: Inflammatory condition - Associated cancer
Colitis/Crohn’s disease - Colon cancer
HPV - Cervical cancer
Hepatitis/Cirrhosis - Liver cancer
Acid reflux - Esophageal cancer
Gastritis - Stomach cancer
Chronic pancreatitis - Pancreatic cancer
How have the hallmarks of cancer changed from the years 2000 to now days?
2000s → Very intrinsic to tumour cells
Ex: evading apoptosis, self-sufficiency of growth signals, limitless replicative potential, etc.
2011 → Start of the releveance of immunology in cancer
Ex: Dregulating cellular energetics, Avoiding immune destruction, tumor-promoting inflammation
2022 → Relevance of non-humane components
Ex: Microbiome, microbes, metabolite availability, epigenetic reprogramming, etc.
What was shown by comparing brain cancer outcomes when targetting tumor cells with radiation vs macrophages?
Targeting macrophages was much more efficient and showed much greater survival → shows the immune microenvrionment matters!!
- Targetting meaning, inhibiting their reruitment
- Tumor-associated macrophages often support tumor growth by promoting angiogenesis, suppressing anti-tumor immunity, and aiding invasion
What is included in the tumor immune microenvrionment?
Everything in the tumour expect tumours cells:
- ECM
- Very present for structure and to allow cells to migrate along these filaments
- Treatments target to block ECM production - Immune cells
- Tissue-resident and recruited - Fibroblasts (producing the ECM)
- Cytokines & Soluble factors
- Vascular inflammation
- Delivers O2 and nutrients to the tumour
- Leaky vasculature allows immune cells to migrate into the tumor
*Often an very early that a patient has cancer is their blood work being all over the place
In a tumor microenvrionment → tumor hypoxia, pH changes, changes in metabolic factors
How is the tumor immune microenvrionment regulated by mutations?
- Different genetic mutations in 3 different tumors of the same cancer (3 patients) → different cytokines release, nutrients, chemokines, immune cells recruited, etc. → different microenvrionments
- Mutational status of the tumor is heterogenous:
1 tumor/1 patient → multiple different mutations → regional differences in microenvrionments / Heterogenous tumor microenvrionment
How is the tumor immune microenvrionment time-dependent?
- Early stages vs Late stages of tumor
- Tumor initiation associated with lower innate response (T cells encountering pathogen for 1st time → generate a response)
- Malignancy/later stages → Depletion/exhaustion of lymphocytes → higher innate response to compensate - Circadian component of the immune system affects the tumor microenvrionment
- Neutrophils are very important for metastatic sucess and have a strong circadian component (Prometastatic neutrophils vs antimetastatic neutrophils
How are different general ways the immune microenvrionment can be targetted in cancer?
- Control ECM remodelling
- ex: inhibitors against MMPs (matrix metalloproteinases), cathepsins, etc. - Target innate immune cells
- ex: CSF-1R inhibitors, DC vaccines - Boost T cell activation
- ex: immune checkpoint inhibitors - Target cytokines to reduce inflammation
- Prevent immune cell recruitment
- ex: block IL8 or CCL2 - Vascular normalization (restoring the abnormal structure and function of tumor blood vessels to a more normal state)
For checkpoint inhibitors, what factors dictate therapeutic efficacy at the tumor level?
- Location of T cells in the tumor
- Expression of PD-1/PD-L1
3 Cases:
a) Infiltrated-excluded (T cells are exluded to the periphery of the tumor, no direct access to tumor cells to kill them) → Poor response to immunotherapy
b) Infiltrated-inflamed (T cells are expressing PD-1 and infiltrated within the tumor cells of the tumor) → Stronger response to immunotherapy
c) Infiltrated-TLS (development of tertiary lymphoid structures, specialized supply of lymphocytes)
There is currently research to figure out how to change an excluded microenvironment into an inflamed microenvrionment
What is the effect of Mismatch repair deficiencies (dMMR) in cancer prognostics?
MMRd → increase risk of development of cancer in multiple organs due to a higher rate of accumulation of mutations
Normal tissues:
- DNA MMR complex finds/repairs genetic mismatches that occur during replication → prevent accumulation of mutations
dMMR tumors:
- DNA mismatches are not fixed → mutations accumulate at higher rates in replicating cells (ex: tumor cells)
- Overtime, these tumors accumulate thousands of mutations → high abundance of immune cells + more likely to recognise the neoantigens because of the high number of mtuations present within the tumor cells (→ “infiltrated-inflamed”)
“Make cancer worse to make it better” → better responders to checkpoint blockade immunotherapies
How do we call the ensemble of factors that dictate therapeutic efficacy?
Exposome - The physiological state of the host (baseline)
- Genetic make up
- Infection history ( → education of the innate and adaptative immune systems)
- Lifetime exposures to cigarette smoke
- Gut microbiome
- Circadian rhythms
- Sex / Age
- Obesity
How does obesity affect cancer?
Obesity is associated with increased RISK of 13 types of cancer, and increased DEATH from 14 types of cancer
*Responsible for 20% of all cancer related deaths
What metric is used to measure obesity? What are its advantages and disadvantages?
BMI as a measure/predictor of metabolic syndrome (not perfect!)
Advantages:
- Easy (weight and height)
Disadvantages:
- Calculation is biased (made up on white men), can change with sex, country, etc. → lots of disparities in healthcare
- Not everyone with an “obese” BMI will have metabolic syndrome and vice versa, people with a “lean” BMI could suffer from metabolic syndrome
How does metabolic obesity regulate cancer?
Adipose tissue and chronic low-grade inflammation:
Obesity = hypertrophy & hyperplasia of adipocytes (eventually dye) → DAMP release → innate immune activation → systemic inflammation / cytokine storm
Release of adipokines, pro-inflammatory cytokines, etc.
This will disrupt homeostasis in lymphoid organs which can become metastatic organs
What are systemic consequences of obesity/metabolic syndrom?
Innate immune system:
- Peripheral expansion of inflammatory neutrophils and monocytes
- Formation of crown-like structures in adipose tissue
- Elevation in pro-inflammatory mediators in serum (e.g. adipokines, cytokines, FFA, cell-free DNA, etc)
Adaptive immune system:
- Reduced frequences of T cell progenitors in thymus
- Accelerated thymic aging
- Reduced thymic lymphopoiesis
- Reduced T cell receptor diversity
- Impaired T cell bioenergetics
- T cell exhaustion
Other immunological effects:
- Accumulation of ectopic adipocytes in bone marrow leading to impaired hematopoiesis
- Dysbiosis and leaky gut
- increased LPS
- Fatty liver
- Splenomegaly, etc…
*Lots of parallels between physiological aging and chronic obesity
How does immunotherapy efficacy vary between obese and lean cancer patients?
Anti-PD1 shows better response in obese cancer patients vs lean
*men also respond better than women
Obesity-driven T cell exhaustion in peripheral circulation → more PD-1+ T cells → anti-PD-1 has a larger effect on the T cell population
What causes cell exhaustion in obese hosts?
- Increased inflammation
- Decreased metabolic control
- Decreased vascular function
- Hormonal changes
Obesity results in decreased leptin sensitivity, leading to more hunger, despite high energy stores
→ In obesity models, T cells work better without leptin signalling (T cells express the leptin receptor), but obesity increases leptin signaling
How can lifestyle influence the tumor immune microenvrionment?
Exercise → increase in levels of stress hormones:
Epinephrine → increased intramural NK cell infiltration, effect on macrophages
Lactate → activation of CD8+ lymphocytes
What are possible effects of diet / obesity on the gut and on cancer?
What experiment showed the effect of the gut on cancer?
Different diets → different body weights
Different diets → different rates of primary tumor growth
Fecal microbiota transplantation (FMT)
1. Take mice that were given antibiotics (not microbiome)
2. Given FMT from patients who had cancer and received immunotherapy (responders vs non-responders) → different microbiomes were given to the mice
3. Mice that were given FMT from responders → responded to immunotherapy and patients who were given FMT from non-responder did not respond
4. Non-responders that were given a specific bacteria by oral gavage started responding
Some specific microbes are required for immunotherapies !!!
How can aging influence the tumor immune microenvrionment?
At older age, more inflammation, more immunosenescence
Young microenvironment → Aged microenvrionment
- Inflammaging
- Immunosenescence (reduced effector immune cell function)
- Increased infiltration of immunosuppressive immune cell populations enabling tumor cell protection from effector immune cell populations (MDSC = myeloid-derived suppressor cells)
- Aged microenvrionment permits growth-permissive primary sites and premetastatic niches
what are the different scales at which cancer can be influenced in other ways than just mutations?
- Single cancer cell
- Tumor microenvrionment (mutations, hypoxia, vascularity, ECM, etc. → intra- and inter- patient heterogeneity)
- Tissue environment (chronic inflammatory conditions, tissue-specific cell types)
- Systemic envrionment (ex: obesity, diet/microbiome, aging, hormone status, sedentarity)
- Lifestyle/host envrionment (ex: envrionmental exposures such as UV, cigarette smoke, pollution, etc.)
How is balance between reactivity and tolerance to self important in the case of cancer?
Some cancer cells are very different from self, but some are also very similar to self → both need to be recognized and killed
- But without killing self
What are the different types of tumor antigens?
- Self-antigens → expressed in healthy tissues
- Tumour-associated antigen (TAA) → aberrant expression on tumor cells, but not exclusively expressed on cancer cells
Ex: over-expression of a tissue-specific protein, mis-expression of a self-protein
Ex: CTAs (cancer testis antigens) are often targeted - Tumour-specific antigen (TSA) → expressed only by tumour cells, not expressed on healthy cells
Ex: peptide from oncovirus, peptide from mutated proteins (neoantigens)
- can be 1 single AA, but in a very specific spot which makes it very immunogenic → The mutation possibly caused that tumour
What is the process of the IDEAL anti-tumour T cell response?
What is the effect of depleting T cells in a tumor?
- Release of tumor antigens
- Antigen presentation to DCs (resident in the tissue) → dLN
- T cell priming and activation
- Proliferation and trafficking of T cells → peripheral blood
- T cell infiltration into tumour site
- Recognition and killing of tumour cells
Subcutaneous tumor injection in mice + anti-CD8 depletion to remove all cytotoxic T cells → much high tumor growth rate than in the presence of T cells
- T cells play a role in control growth rate of some tumours (not all tumours, mostly very immunogenic tumours)
What are 2 important reasons why tumour specific T cells are not able to kill the whole tumours ?
- The tumour immune microenvrionment is very immunosuppressive
- T cells get exhausted
What are phenotypical differences between Activated T cells and Terminally exhausted T cells?
Activated → Terminally exhausted:
High → reduced proliferation
High → reduced cytotoxicity (killing activity)
High → reduced effector cytokine production
Low → Elevated levels of inhibitory receptor expression/inhibitory molecules
What are the 2 large classes of T cell-based immunotherapies?
- Activate endogenous anti-tumour T cells
- Re-envigorate T cells already present - Deliver a bolus of tumor-specific T cells
- Often autologous T cells
What are the different T cell “checkpoint” molecules?
What are 2 functions of co-inhibitory molecules?
Co-signaling molecules positively/negatively regulate T cell function:
- Immunoglobulin superfamily (Ig)
- Tumor necrosis factor receptor family (TNFR)
Co-inhibitory molecules are expressed naïve and activated T cells:
- Maintain quiescence at steady-state
- Limit the T cell response (ex: PD1-1, CTLA-4)
*Checkpoint inhibitors block co-inhibitory molecule function → reinvigorate an anti-tumor T cell response
Great clinical responses, but not for all patients + accompagnied by adverse immune events
Where are co-inhibitory ligands expressed?
Expressed on diverse cell types and interact with receptor on T cells:
- Antigen presenting cells
- Non-hematopoietic cells (tissue-specific cells)
- Cancer cells
What are important features of CTLA-4
CTLA-4 = Cytotoxic T lymphocyte associated protein 4
- Ig superfamily member
- Upregulated on activated T cells
- Constitutively expressed at high levels on Tregs (important role in Treg function)
Inhibit T cell function through multiple mechanisms:
- Inhibit CD28 binding to CD80/86 (B7-1/B7-2)
- Dephosphorylation of TCR/CD28 proximal signaling intermediates
What is CTLA-4’s ligand?
CD80/86 (B7-1/B7-2) → blocks co-stimulatory signal
What phenotype is seen in CTLA-4 KO mice? vs PD-1 KO mice?
CTLA-4 KO mice die within ~3-10 weeks of birth due to massive T cell proliferation and tissue infiltration
- Lymph nodes in KO mice undergo massive expansion (no break to T cell expansion)
PD-1 KO mice have a less severe phenotype than CTLA-4 KO mice, but eventually sucombe to T cell infiltration
- Mostly in organs where PD-L1 expression is high, for ex: the heart
PD-L1 KO show an even milder phenotype
What are consequences/effects of anti-CTLA-4 treatment?
Most commonly used = Ipilimumab
- Not specifically tumor cell-specific
Treg cells express high levels of CTLA4 and are more prone anti-CTLA4- induced antibody-dependent cellular cytotoxicity (ADCC)
→ Anti-CTLA4 prevents Treg from inhibiting conventional T cell activity
Anti-CTLA-4 blocks “the brake” on conventional T cell activity
What are important features of PD-1?
How does it affect T cell activity?
PD-1 = programmed cell death protein 1
- Ig superfamily member
- Upregulated on activated T cells (to dampen down the response)
Binds to PD-L1 and PD-L2 expressed on antigen presenting cells, other tissue cells (e.g., heart, kidney), and cancer cells
Inhibits T cell (and B cell) function via dephosphorylation of T cell receptor/co-stimulation signaling intermediates
What are consequences/effects of anti-PD-1/ anti-PD-L1 treatment?
What are the names of the specific drugs?
Anti-PD-1: Nivolumab, Pembrolizumab, etc.
Anti-PD-L1: Atezolizumab, etc.
Anti-PD-1 or anti-PD-L1 blocks the interaction between PD-1 on the T cell with the inhibitory ligand expressed on antigen presenting cells, cancer cells (and other tissue cells)
*We can block the ligand unlike CTLA-4
Which cancers are most often treated with immunotherapies?
Melanomas (liquid cancers, in the blood)
Lung cancer
How are immune related adverse events associated with chickpoint inhibitors?
Mild IRAE are an indication that the treatment is working and the T cells are activated
Severe IRAE might lead to interruption of the treatment
- More severe IRAE with CTLA-4 treatment
- Mostly in tissues exposed to the envrionment (skin, gut, lungs)
How is the tumour mutation burden correlated to response rate?
Which cancers are generally better treated with checkpoint inhibitors?
Positive correlation → Increased tumour burden ~ increased response rate to checkpoint blockade treatments
Increased neoantigen → higher immunogenic potential → bigger T cell pool present in the tumour to be reinvigorated by checkpoint blockade
Colorectal cancer → dMMR (high mutation burden)
Melanomas
Lung cancer
How can neoantigens from a patient’s cancer be identified for further immunotherapies?
- Sample acquisition (from solid tumor or PBMC)
- Comparative sequencing and mutation identification
- Neoantigen prediction and target prioritization (algorithms to predict which peptides wil be better processed and presented on HLA → quality of these algorithms is very important)
- Algorithms are biased as they are trained mostly with HLA-0202
- All presented peptides are not necessarily immunogenic so have to predict both - Vaccin design and on-demand production
- Idenividualized poly-specific neoantigen vaccine
- Vaccine-induced priming
- Tumour cell recognition and killing
All patients may be able to elicit an immune response, but still will not all respond to mRNA cancer vaccines for ex:
- patients that respond did not necessarily have the greatest number of neoantigens
- not all neoantigens included in the vaccine elicited a T cell response (~25%)
- responders had significantly delayed pancreatic cancer recurrence
What are 3 general types of cancer vaccines?
- Cell-based cancer vaccines
- Peptide is loaded onto APCs and delivered to be presented
- Tumor-associated antigens - Peptide-based cancer vaccines
- Cancer epitopes of interest are delivered to the immune system as peptides to be uptaken and presented - Nuclei acid-based cancer vaccines
- DNA or RNA encoding tumor antigens are delivered to the immune system
In general, what are adoptive cell therapies?
A type of immunotherapy in which T cells are given to a patient to help the body fight diseases, such as cancer.
T cells are usually taken from the patient’s own blood or tumor tissue, grown in large numbers in the laboratory, and then given back to the patient to help the immune system fight the cancer.
Sometimes, the T cells are changed in the laboratory to make them better able to target the patient’s cancer cells and kill them.
Also known as: adoptive cell transfer, cellular adoptive immunotherapy, and T-cell transfer therapy.
What are the different types of adoptive cell therapies?
- Tumour infiltrating lymphocytes (TIL)
- Antigen-specific T cell therapy
- T cell receptor-engineered T cells (TCR-T)
- Chimeric antigen receptor T cells (CAR-T)
What are Tumour infiltrating lymphocytes (TIL)?
What are pros and cons?
- Lymphocytes are harvest from a tumour
- Non-sepcific expansion of the T cells (ex: IL-2 + anti-CD3/28)
- Expanded T cells are reinfused into the patient (+ IL-2 for T cell expansion)
Pros → Patients own cells, no donor match needed, many of the T cells isolated from the tumour (not all) will be tumour specific
Cons → Not all tumours have significant T cell infiltration, some T cells in the tumour are terminally exhausted
First clinical trials = 1980s
First FDA approved TIL therapy = 2024
What is antigen-specific T cell therapy?
Expansion of tumour-specific T cells from peripheral blood using tumour-lysate or known tumour-antigen loaded antigen presenting cells (derived from the same donor)
- Prime and expanded tumour specific T cells in vitro by presenting them with tumour-specific antigens
- Re-inject the enriched antigen-specific T cells
Pros → patients own cells, no donor match needed
Cons → need a known tumour antigen (if not using lysate), multiple rounds of expansion can lead to T cell dysfunction
What is an example of an application of Antigen-specific T cell therapy?
Epstein-Barr Virus-driven cancer:
- We know many of the immunogenic peptides so we can use them to prime T cells
What are T cell receptor-engineered T cells?
By knowin our target, we can engineer T cells specific to that target.
Target = peptide derived from a TSA or TAA (tumour specific or tumour associated antigen) presented in the context of MHC
- Isolate T cells (from patient
- T-cell activation & expansion
- TCR engineering
- Quality control & amplification
- TCR T-cell transfusion back into patients
*Need the MHC context and a TCR that can target those MHCs
What are chimeric antigen receptor T cells (CAR-T) ?
Engineer a chimeric antigen receptor (synthetic receptor) which has an Ab-like extracellular domain + TCR signal components in intracellular domain
Target = cell surface TAA or TSA (has to be cell surface since no MHC), antigen-specific
Pros → no MHC restriction
Cons → only for cell surface antigens
Co-stimulatory endodomains influence the kinetics and persisitence of the response → CD28 and 4-1BB costimulation
What types of cancers/antigens are targetted by most FDA-approved CAR T cell therapies?
Mostly targetting B cell lymphomas → specifically CD19 (specific B-cell expression)
Much easier to target liquid cancer for tumor cell access
What are mechanisms of immune evasion?
- downregulation of T cell targets
- Some B cells downregulate CD19 (CAR T cell target)
- Downregulation of MHC / expression of non-classical HLA molecules
